In general, a radiation generating tube accelerates electrons emitted from an electron emitting source to high energies and irradiates a target including a metal, such as tungsten, with the high energies to generate radiations such as X-rays. The generated radiations are emitted in all directions. Therefore, in order to shield unnecessary radiations, a container is provided to house the radiation generating tube or the radiation generating tube is surrounded by a shield (radiation shielding member) such as one including lead to prevent external leakage of the unnecessary radiations. Thus, such radiation generating tube and such radiation generating apparatus that houses the radiation generating tube therein have a difficulty in size and weight reduction.
As a solution for this problem, Japanese Patent Application Laid-Open No. 2007-265981 discloses a method in which a shield is arranged on each of the radiation emission side and the electron entrance side of a target in a transmission type radiation generating tube to shield unnecessary radiations with a simple structure as well as providing reduction in size and weight of the apparatus.
However, in general, in such transmission type radiation generating tube to which a target, i.e., an anode is fixed, the target does not necessarily sufficiently radiates heat because of the effect of local heat generated in the target, resulting in difficulty in generation of high-energy radiation. Regarding the target's heat radiation, PTL 1 describes that the transmission type radiation generating tube described therein has a structure in which a target and a shield are joined to each other, thereby heat generated in the target being radiated as a result of being transferred to the shield, enabling suppression of an increase in temperature of the target.